H3 Clogged cat?

[lowtrac]

I've had a P0420 code for several months now. I replaced the rear o2 sensor a few weeks ago but it didn't fix it.


Yesterday on the way home I noticed a different exhaust sound. It sounded deeper and little louder than normal. Once I got to the highway it seemed to be down on power, like a lot. It will get up to to speed, but struggles way worse than usual. Transmission seems to be shifting normally. I figure it may have a clogged cat. Not sure which one but I hope it's the back one since that's easier to deal with. Anyone else had a similar issue? I'm going to try to get it pulled out this weekend and see if I can tell anything.

 

[ludevick]

Most common problem I’ve heard of with the exhaust is the exhaust manifold that is integrated with the catalytic converter. It’s cast iron and it tends to crack.
This happened to me and I noticed that it was down on power and loud, like you described , but also had a distinct hissing/ tapping sound when cold. I could also smell the exhaust quite a bit.

 

[adventuredad]

Most common problem I’ve heard of with the exhaust is the exhaust manifold that is integrated with the catalytic converter. It’s cast iron and it tends to crack.
This happened to me and I noticed that it was down on power and loud, like you described , but also had a distinct hissing/ tapping sound when cold. I could also smell the exhaust quite a bit.

I just got my H3 a couple weeks ago and I notice a ticking sound for the first few minutes after starting it. I figured it was an exhaust leak but you’ve got me wondering if it’s the header. How big a deal is it to fix? Can you simply replace the header or does that come with many more challenges?
I also have a mangaflow muffler that someone garbled together just after the joint in the pipe under the truck. I don’t care for the loud exhaust on it, it’s no sports car that I’m trying to show off with.


Sent from my iPhone using Tapatalk

 

[ludevick]

Sadly, I live in California so the emissions regulations are very strict. If you live here and want to be able to smog the car you’re essentially going to have to go with an OEM manifold/ cat. This ran me a little under $1000 including $100 for install. If you don’t live in California i believe you can get a decent header for around $250.
Another common problem is the bolts that hold the manifold in place are known to seize/ crack/ shear off which can make it a PITA to get the manifold off, or cause a leak. I was lucky and they said the bolts were in good shape.


Sent from my iPhone using Tapatalk

 

[Zach]

Sadly, I live in California so the emissions regulations are very strict. If you live here and want to be able to smog the car you’re essentially going to have to go with an OEM manifold/ cat. This ran me a little under $1000 including $100 for install. If you don’t live in California i believe you can get a decent header for around $250.
Another common problem is the bolts that hold the manifold in place are known to seize/ crack/ shear off which can make it a PITA to get the manifold off, or cause a leak. I was lucky and they said the bolts were in good shape.


Sent from my iPhone using Tapatalk

There are ways around it if you live in California. As long as it looks like the stock part, they won’t balk at it. Businesses won’t sell to someone in California. If you have someone buy it out of here and ship it to you it works. Did that with my beater daily car.

 

[alrock]

I just got my H3 a couple weeks ago and I notice a ticking sound for the first few minutes after starting it. I figured it was an exhaust leak but you’ve got me wondering if it’s the header. How big a deal is it to fix? Can you simply replace the header or does that come with many more challenges?
I also have a mangaflow muffler that someone garbled together just after the joint in the pipe under the truck. I don’t care for the loud exhaust on it, it’s no sports car that I’m trying to show off with.

Sent from my iPhone using Tapatalk

Stick with the OEM exhaust manifold if you're not looking for "upgrades". It fits (which some aftermarket ones have fitment issues) and as cast iron it absorbs some of the noise. It's a bit of project to replace and you have to be careful about breaking off bolts - heck, that could be part of the sound that you're hearing.

We (meaning Reloader) did it at his house but he's got the benefit of a lift and years of experience.

It's a good time to replace that passenger side motor mount as well since it does tend to fail.

New OEM

"Slight" crack in the old unit

 

[adventuredad]

Stick with the OEM exhaust manifold if you're not looking for "upgrades". It fits (which some aftermarket ones have fitment issues) and as cast iron it absorbs some of the noise. It's a bit of project to replace and you have to be careful about breaking off bolts - heck, that could be part of the sound that you're hearing.

We (meaning Reloader) did it at his house but he's got the benefit of a lift and years of experience.

It's a good time to replace that passenger side motor mount as well since it does tend to fail.

Slight crack huh? That looks like a pretty major crack, I bet it got a little loud under the hood. I'm going to try and dig into it this weekend a little and see if I can at least inspect the manifold for any trouble. There's actually room around the engine which is actually nice but I don't want to tackle that one unless I have too. You sure are lucky to have Reloader around huh?

 

[scoreh3]

Mine did that too.

 

[lowtrac]

I cut the rear cat out this afternoon. The stuff inside rattles around a lot and if you shake it some stuff comes out. I shined a flashlight in one end and couldn’t see it from the other. I stuck a piece of pipe in there for now until I decide whether or not to get a universal cat welded in or get a replacement pipe.

Sent from my iPhone using Tapatalk

 

[lowtrac]

I drove for about 75 miles today, mixed highway and regular roads. That was definitely the issue. It doesn’t feel like I’m towing a trailer anymore.

Has anyone gone with a universal cat replacement? I had a Cadillac Seville a while back that no muffler shop would touch as far as cats go. They said they were too finicky and still wouldn’t pass emissions tests with aftermarket cats.


Sent from my iPhone using Tapatalk